Severe Weather Outbreak Forecast Wednesday (Updated 415 pm CDT)

...SEVERE THUNDERSTORMS EXPECTED OVER PARTS OF THE NORTHERN PLAINS
LATE AFTERNOON THROUGH TONIGHT...

THE NWS STORM PREDICTION CENTER IN NORMAN OK IS FORECASTING THE
DEVELOPMENT OF WIDESPREAD DAMAGING WINDS OVER PARTS OF THE NORTHERN
PLAINS LATE AFTERNOON THROUGH TONIGHT.

THE AREAS MOST LIKELY TO EXPERIENCE THIS ACTIVITY INCLUDE

CENTRAL AND SOUTHERN NORTH DAKOTA
MUCH OF SOUTH DAKOTA

ELSEWHERE...SEVERE STORMS ALSO ARE POSSIBLE FROM EASTERN MONTANA
ACROSS THE REMAINDER OF THE NORTHERN PLAINS THIS AFTERNOON AND
EVENING...AND SOUTHEASTWARD ACROSS PARTS OF THE LOWER MISSOURI
VALLEY REGION OVERNIGHT.

A MIDDLE-UPPER LEVEL TROUGH IS EXPECTED TO MOVE FROM THE PACIFIC
NORTHWEST ACROSS THE NORTHERN HIGH PLAINS THIS AFTERNOON AND
EVENING. MEANWHILE A RELATED COLD FRONT SHOULD PROGRESS EASTWARD
ACROSS THE DAKOTAS INTO A PROGRESSIVELY MORE MOIST AND UNSTABLE AIR
MASS. THUNDERSTORM POTENTIAL WILL REMAIN SUPPRESSED MOST OF THIS
AFTERNOON BY A STRONG CAPPING INVERSION OF WARM AIR ABOVE GROUND
LEVEL. NONETHELESS...BECAUSE OF THE FAVORABLE LEVELS OF
MOISTURE...INSTABILITY...LIFT AND WIND SHEAR...WE EXPECT THIS CAP TO
BREAK OVER PARTS OF THE NORTHERN HIGH PLAINS AND DAKOTAS...PERHAPS
AS EARLY AS LATE AFTERNOON.

SUPERCELLS WITH LARGE HAIL...SEVERE THUNDERSTORM WIND AND A FEW
TORNADOES ARE POSSIBLE AT FIRST. THEN...SEVERE STORMS SHOULD GET
MORE NUMEROUS THIS EVENING...GROWING INTO A COMPLEX WITH POTENTIAL
FOR A WIDESPREAD AND LONG-LASTING THUNDERSTORM WIND DAMAGE EVENT
KNOWN AS A DERECHO. THE GREATEST THREAT AREA APPEARS TO BE OVER
PARTS OF THE DAKOTAS. FOR MORE METEOROLOGICAL DETAILS PLEASE SEE
THE SPC CONVECTIVE DAY-1 OUTLOOK...WHICH IS BEING UPGRADED TO
WIND-BASED MDT RISK TO REFLECT THE THREAT.

STATE AND LOCAL EMERGENCY MANAGERS ARE MONITORING THIS DEVELOPING
SITUATION. THOSE IN THE THREATENED AREA ARE URGED TO REVIEW SEVERE
WEATHER SAFETY RULES AND TO LISTEN TO RADIO...TELEVISION...AND NOAA
WEATHER RADIO FOR POSSIBLE WATCHES...WARNINGS...AND STATEMENTS LATER
TODAY.